Question text - rich text font size change does not reflect in preview / published survey

Hi,
I would like to put a short guide (a few lines of text) bellow each question.
I would like this text to be smaller than the question text

To do that, I edited the question text on 'rich content editor' and modified the size of the 'guide' text.

This change does not show on the preview or published survey.
The font size remains the one from the Look&Feel "question font size" style that seems to bypass all the rich text editions.

In qualtrics documentation, it seems to say that local rich text changes should bypass global look&feel settings.

Am I doind anything wrong?
Is there another way I should do ?

Thanks in advance for your help.
Have a nice day
Nicolas